1. Field of the Invention
The present invention is related to the production of desalinated water from seawater or other sources of water contaminated with saline. More particularly, the present disclosure relates to a system of producing desalinated water from a saline contaminated water source through a low water recovery desalination system
2. Related Art
Desalination systems are desirable in many arid regions and in marine applications where fresh water supplies are limited but large amounts of seawater, inland waterways, rivers, or other sources of salt containing water are available.
Conventional desalination systems utilize reverse osmosis or distillation processes. Both of these processes typically result in recovery ratios of approximately 50%. Thus for every gallon of water taken in as feed ½ of a gallon will become purified product water and the other ½ gallon will be discharged with a brine content approximately double in concentration of the feed water's concentration. Discharge of this concentrated brine to the environment can produce localized negative impacts. Reverse osmosis and distillation processes operate at high recovery ratios in order to reduce specific power consumption. This is required because in conventional systems all of the feed is either heated, as in the case of distillation, or pressurized as in the case with reverse osmosis.
The maximum recovery rate conventional systems can operate at is usually limited by the tendency of the feed waters to form scaling deposits. Scale forming compounds, such as calcium and silica, can precipitate on the membranes or heat transfer surfaces of the primary desalination system. This can result in costly equipment replacements or cleaning. The tendency to form scale is a function of the maximum concentration of scale forming materials in the concentrated brine, which is in turn determined by the feed concentrations of these solutes and the system water recovery ratio. Due to composition, this typically limits the recovery ratio in most seawater desalination applications to about 50%.
Additionally, due to the need to operate at high recovery rates, feed pretreatment is usually required. Existing pretreatment methods produce solid wastes that are usually disposed of in landfills and may contain hazardous contaminates such as heavy metals. Conventional desalination systems also kill most organisms entrained in the feed and produce a brine byproduct that is high in salts and toxic to most organisms.
Although conventional desalination systems exist, there are no systems available which efficiently operate at water recovery rates low enough to produce a brine that is environmentally benign. There is also a need for systems which do not produce solid wastes and which reduces or eliminates the kill rate of entrained marine organisms in the feed water.
What is needed is a low water recovery rate desalination system that reduces the negative environmental impacts of desalination.